Catalyst for reforming

ABSTRACT

The present invention relates to a catalyst for reforming that is employed when preparing a synthetic gas by reacting hydrocarbon such as methane with a reforming agent such as water, carbon dioxide, oxygen, air or the like. The present invention further relates to a process for producing a synthetic gas employing this catalyst for reforming. By employing the catalyst for reforming that is a mixed oxide having the composition expressed by the following formula in which the M and Co are in a highly dispersed state, it is possible to suppress precipitation of carbonaceous matters (carbon) when producing the synthetic gas. 
     
       
         aM.bCo.cMg.dCa.eO 
       
     
     (Where, a, b, c, d, and e are molar fractions, a+b+c+d=1, 0.0001≦a≦0.10, 0.0001≦b≦0.20, 0.70≦(c+d)≦0.9998, 0&lt;c≦0.9998, 0≦d&lt;0.9998, e=the number of oxygen necessary to maintain an electric charge balance with metallic elements. M is at least one type of element selected from among the group VIA elements, group VIIA elements, group VIII transition elements excluding Co, group IB elements, group IIB elements, group IVB elements and lanthanoid elements in the periodic table.)

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a catalyst for reforming that isemployed when producing synthetic gas by reacting hydrocarbon such asmethane with a reforming agent such as water, carbon dioxide, oxygen,air or the like. The present invention further relates to a process forproducing synthetic gas employing this catalyst for reforming. Thesynthetic gas is a mixed gas containing carbon monoxide (CO) andhydrogen (H₂).

The present specification is based on a patent application filed inJapan (Japanese Patent Application No. Hei. 11-98220), the contents ofwhich are incorporated herein by reference.

2. Description of the Related Art

It has been the conventional practice to carry out reforming by reactinghydrocarbon such as methane, natural gas, petroleum gas, naphtha, heavyoil, crude oil or the like, and a reforming agent such as water, air,oxygen, or carbon dioxide at high temperature in the presence of acatalyst, to generate a highly reactive synthetic gas. Methanol orliquid fuels are then produced by employing this generated synthetic gasas a source material.

Ni/Al₂O₃ catalyst, Ni/MgO/Al₂O₃ catalyst or the like may be applied asexamples of reforming catalysts used in reforming reactions.

However, when stoichiometric equivalents of methane and steam arereacted during reforming employing these types of catalysts forreforming, for example, a problem arises in that considerable depositionof carbonaceous matters (carbon) occurs. Accordingly, in order toprevent deposition of this carbonaceous matters, a large excess of steamis supplied to the reactor, to accelerate the reforming reaction.

As a result, reforming reactions as conventionally performed requires alarge amount of steam, leading to such undesirable consequences asincreased energy costs and larger facilities.

SUMMARY OF THE INVENTION

It is the objective of the present invention to prevent the depositionof carbonaceous matters when producing synthetic gas by adding astoichiometric equivalent, or an amount near the stoichiometricequivalent, of a reforming agent to hydrocarbon.

This subject can be resolved by employing a compound that is a mixedoxide having the composition expressed by the following formula in whichM and Co are more highly dispersed as the catalyst for reforming.

aM.bCo.cMg.dCa.eO

(Where, a, b, c, d, and e are molar fractions, a+b+c+d=1, 0.0001≦a≦0.10,0.0001≦b≦0.20, 0.70≦(c+d)≦0.9998, 0<c≦0.9998, 0≦d<0.9998, and e=thenumber of oxygen necessary to maintain an electric charge balance withmetallic elements. M is at least one type of element selected from amongthe group VIA elements, group VIIA elements, group VIII transitionelements excluding Co, group IB elements, group IIB elements, group IVBelements and lanthanoid elements in the periodic table.)

The present invention employs as the catalyst for reforming the mixedoxide in which M and Co are more highly dispersed. As a result, evenwhen reacting the stoichiometric equivalent, or an amount near thestoichiometric equivalent, of the hydrocarbon and the reforming agent,it is possible to suppress deposition of carbonaceous matters (carbon).Accordingly, the synthetic gas can be obtained with high efficiency, andproduction costs can be reduced. Moreover, the catalyst is notcontaminated by the carbonaceous matters, so that deterioration incatalytic activity over time is prevented, and the life of the catalystcan be extended.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an explanatory figure schematically showing the surfacecondition of the catalyst in the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will now be described in detail.

The present invention's cobalt-type catalyst for reforming shall beexplained first.

The present invention's cobalt-type catalyst for reforming comprises ofa mixed oxide having the composition expressed by the formula below. Thecomposition here is expressed as an anhydride basis after calcination.

aM.bCo.cMg.dCa.eO

(Where, a, b, c, d, and e are molar fractions, a+b+c+d=1, 0.0001≦a≦0.10,0.0001≦b≦0.20, 0.70≦(c+d)≦0.9998, 0<c≦0.9998, 0≦d<0.9998, e=the numberof oxygen necessary to maintain an electric charge balance with metallicelements. M is at least one type of element selected from among thegroup VIA elements, group VIIA elements, group VIII transition elementsexcluding Co, group IB elements, group IIB elements, group IVB elementsand lanthanoid elements in the periodic table.)

Note that the periodic table cited here is based on the IUPAC.

It is preferable that M be at least one element selected from the groupcomprising manganese, rhodium, ruthenium, platinum, palladium, zinc,lead, lanthanum, and cerium. In this composition, the M content (a) is0.0001≦a≦0.10, preferably 0.0001≦a≦0.05, and even more preferably0.0001≦a≦0.03. When the M content (a) is less than 0.0001, then theeffect of suppressing deposition of the carbonaceous matters is notsufficient. When the M content (a) exceeds 0.10, there is anundesirable. drop in the activity of the reforming reaction.

The cobalt content (b) is 0.0001≦b≦0.20, preferably 0.0001≦b≦0.15, andeven more preferably 0.0001≦b≦0.10. When the cobalt content (b) is lessthan 0.0001, then the content of cobalt is too small and the activity ofreactions falls. When the content exceeds 0.20, the higher dispersion ofcobalt described below is hindered, and the deposition of thecarbonaceous matters cannot be sufficiently suppressed.

The total amount (c+d) of the magnesium content (c) and the calciumcontent (d) is 0.70≦(c+d)≦0.9998, preferably 0.85≦(c+d)≦0.9998, and evenmore preferably 0.90≦(c+d)≦0.9998. Of this total amount, the magnesiumcontent (c) is 0<c≦0.9998, preferably 0.35≦c≦0.9998, and even morepreferably 0.6≦c≦0.9998, while the calcium content (d) is 0≦d<0.9998,preferably 0≦d≦0.5, and even more preferably 0≦d≦0.3. It is alsoacceptable not to include calcium in the catalyst for reforming.

The total amount (c+d) of the magnesium content (c) and the calciumcontent (d) is determined by the balance with the M content (a) and thecobalt content (b). Provided that (c+d) are within the limits describedabove, then an excellent effect is obtained for the reforming reactionat any ratio. However, although the deposition of the carbonaceousmatters can be sufficiently suppressed if the contents of calcium (d)and M (a) are large, catalytic activity is reduced as compared to thecase where there is much content of magnesium (c). Therefore, whenpreparing a more highly reactive catalyst, it is preferable to fix thecalcium content (c) at less than 0.5, and the M content at less than0.1.

The MgO and CaO in the mixed oxide employed in the present inventionhave rock salt type crystal structure and a portion of each of the Mgand Ca atoms positioned in this lattice is substituted with cobalt andM. Therefore, the mixed oxide employed here is not a mixture of separateoxides of M, cobalt, magnesium, and calcium, but a type of solidsolution.

In the present invention, the cobalt and M exist in a highly dispersedstate in this mixed oxide.

“Dispersion” as employed in the present invention is as usually definedin the catalyst preparation field. For example, as set forth in“Shokubai Koza, Vol. 5, Catalyst Designs”, p. 141 (Shokubai Gakkaihen,Kodanshakan), dispersion is defined as the ratio of the number of atomsexposed on the catalyst surface with respect to the total number ofatoms of the supported metal. In other words, “high dispersion” refersto a state in which this ratio is high.

To explain this concretely for the present invention using the schematicof FIG. 1, innumerable spherical microparticles 2 which form the centerof activity are present on the surface of a catalyst 1 comprising of amixed oxide. Following the activation (reduction) treatment describedbelow, these microparticles 2 consist of the cobalt and M metalelements, and the compounds thereof.

The dispersion ratio may be designated as B/A, where A is the number ofatoms of the cobalt and M metal elements, and the compounds of cobaltand M, and B is the number of atoms from among these that are exposed onthe surface of microparticle 2.

It is believed that the atoms exposed on the surface of microparticle 2participate in the catalyst reaction. Moreover, there are many atomsexposed on the surface in a catalyst in which the dispersion ratio isnear 1. For this reason, it is thought that the center of activity isincreased in a catalyst in which the dispersion ratio is near 1,resulting in high reactivity.

In addition, the majority of the atoms in microparticle 2 will beexposed on the surface of catalyst 1, with the dispersion ratioapproaching 1, if the particle diameter of microparticle 2 becomes smallas possible. Accordingly, the diameter of microparticle 2 may be viewedto be an index expressing the dispersion ratio.

In the present invention's catalyst, the diameter of microparticle 2 isless than 3.5 nm, below the limit of measurement for various methodssuch as X-ray diffraction determination, for example. For this reason,the present invention's catalyst may be deemed to be in a highlydispersed state, with a high dispersion ratio. Accordingly, the numberof cobalt and M atoms participating in the reforming reaction increases,resulting in high reactivity, with the stoichiometrical reactionprogress. Thus, the deposition of carbonaceous matters (carbon) duringthe reforming reaction is prevented.

Any method is acceptable for preparing a reforming catalyst of thistype, provided that it renders cobalt and M into a highly dispersedstate. Particularly preferred methods may be cited, includingimpregnation supporting method, coprecipitation, sol-gel method(hydrolysis method), and homogeneous precipitation. In addition, thecatalyst for reforming may also be prepared using the preparation methoddisclosed in Japanese Patent Application, First Publication No. Hei8-131835 previously submitted by the current applicants.

For example, when using a coprecipitation method to prepare the catalystfor reforming, water soluble salts of cobalt, magnesium, calcium, groupVIA elements, group VIIA elements, group VIII transition elementsexcluding cobalt, group IB elements, group IIB elements, group IVBelements, and lanthanoid elements are dissolved in water, to form anaqueous solution. Organic salts such as acetate and inorganic salts suchas nitrate may be cited as examples of water soluble salts. Aprecipitate is generated by adding a precipitation reagent to thisaqueous solution while stirring at 293˜393 K. In order to highlydisperse the catalyst components, it is preferable to stir whengenerating the precipitate, and to complete formation of the precipitateby continuing to stir for 10 minutes or more following the formation.

Sodium and/or potassium carbonate, hydrogen carbonate, oxalate, orhydroxide are preferred as the precipitation reagent. Ammonia carbonate,ammonia hydroxide, ammonia (aqueous ammonia) and the like may also beused as the precipitation reagent.

The pH increases with the addition of the precipitation reagent, and acompound comprising of the above components precipitates in the form ofa thermally decomposable hydroxide. The final pH of the mixture ispreferably 6 or more, with a pH in the range of 8˜11 being even moredesirable. When the precipitate forms, it is subjected to filtering, andthen repeated washing using water or an aqueous solution of ammoniacarbonate. This is then dried at a temperature of 373 K or more. Next,the dried precipitate is calcinated for 20 hours at 773˜1773 K in air todecompose the thermally decomposable hydroxide, thereby obtaining thetargeted catalyst for reforming.

The thus-obtained catalyst is crushed, and may be employed as a powder.However, it is also acceptable to employ the catalyst molded in tabletform by a compression molding machine as needed. It is also acceptableto employ these catalysts in combination with quartz sand, alumina,magnesia, calcium oxide or other additives.

A process for producing synthetic gas employing this type of catalystfor reforming shall now be explained.

First, an activating treatment of the catalyst for reforming isperformed. This activating treatment is carried out by heating thecatalyst at 773˜1273 K, preferably 873˜1273 K, and more preferably923˜1273 K, in the presence of a reducing gas such as hydrogen gas forabout 1˜120 minutes. The reducing gas may be diluted with an inert gassuch as nitrogen gas. The activating treatment may be carried out in areactor in which the reforming reaction is performed.

As a result of this activating treatment, microparticles 2 on thesurface of catalyst 1 in FIG. 1 are reduced, becoming cobalt or M metalelements, or compounds thereof, and thereby enhancing the catalyticactivity.

In the conventional cobalt oxide type catalyst, the activatingtreatments were all carried out at less than 773 K. In contrast, theactivating treatment in the present invention is carried out at a highertemperature than in the case of the conventional cobalt oxide typecatalyst. This type of activating treatment at high temperature cancontribute to higher dispersion of cobalt and M as described above.

Natural gas, petroleum gas, naphtha, heavy oil, crude oil, orhydrocarbons obtained from coal, tar sand or the like may be employed asthe hydrocarbon that serves as the source material for the syntheticgas. The hydrocarbon employed is not particularly limited, provided thathydrocarbon such as methane is included as a portion thereof. It is alsoacceptable to mix two or more hydrocarbons.

Water (steam), carbon dioxide, oxygen, air or the like may be employedas the reforming agent, with mixtures of two or more of these also beingacceptable.

When the supply rate of the hydrocarbon and reforming agent during thereaction is expressed as a molar ratio in which the number of carbonatoms in the hydrocarbon is set as the standard, typically, reformingagent/carbon ratio is taken as 0.3˜100, preferably 0.3˜10, and even morepreferably, 0.5˜3. In this invention, it is not necessary to supply alarge excess of the reforming agent. An inert gas such as nitrogen maybe present as a diluent in the gas mixture of the hydrocarbon and thereforming agent.

With regard to the specific reaction, the feed-stock gas comprising ofthe hydrocarbon and the reforming agent is supplied to a reactor filledwith the above-described reforming catalyst, and the reaction is carriedout at a temperature of 773˜1273 K, preferably 873˜1273 K and even morepreferably 923˜1273 K, at a pressure of 0.1˜10 MPa, preferably 0.1˜5MPa, and even more preferably 0.1˜3 MPa.

The gas hourly space velocity (GHSV: the value obtained when the supplyrate of the feed-stock gas is divided by the quantity of catalystcalculated as a volume) is 500˜200000 h⁻¹, preferably 1000˜100000h⁻¹,and even more preferably 1000˜70000h⁻¹. The various types of reactorsconventionally known may be optionally employed, including a fixed bed,moving bed, fluidized bed, or the like.

This type of catalyst for reforming is the mixed oxide of CoO and MOxwith MgO or MgO/CaO. Wherein cobalt and M are highly dispersed.Therefore, the catalyst for reforming becomes highly active, so that itis possible to suppress deposition of the carbonaceous matters (carbon)even when the stoichiometric equivalent, or an amount near thestoichiometric equivalent, of the hydrocarbon such as methane and thereforming agent such as steam are reacted. As a result, the syntheticgas can be produced with high efficiency. For this reason, when thistype of catalyst for reforming is employed, it is not necessary tosupply a large excess of the reforming agent such as steam. Thus, thereforming agent is not wasted, and the synthetic gas can be produced atlow cost.

In addition, the catalyst is not contaminated with carbonaceous matters,so that deterioration in catalytic activity over time can be prevented,thereby extending the life of the catalyst.

Embodiments

The actions and effects of the present invention will now be clarifiedusing specific examples. Note, however, that the invention is notlimited thereto.

EXAMPLE 1

(1) Catalyst preparation

3.52 g of cobalt nitrate hexahydrate, 58.3 g of magnesium nitratehexahydrate, and 0.695 g of manganese nitrate hexahydrate were dissolvedin 250 ml of water. Next, 121 ml of 2 mol/L aqueous potassium carbonatewas added to the mixture, to generate a precipitate comprising of thethree components of cobalt, magnesium, and manganese. The precipitatewas filtered and washed, after which it was dried in air at 393 K for 12hours or more. Calcination in air at 1223 K for 20 hours was thenperformed, to obtain a 1 mol % manganese-5 mol % cobalt-magnesium mixedoxide.

(2) Reaction test

The reaction was carried out using a high pressure flow type fixed bedreactor. An activating treatment was performed by filling an aluminareaction tube of inner diameter 4 mm with 0.2 g of the above-describedcatalyst molded to 250˜500 μm, and maintaining it for 60 minutes at 1173K in a hydrogen gas flow. Reaction tests were performed under thefollowing conditions. The reaction products obtained by theabove-described operations were introduced into a gas chromatograph andanalyzed. The methane conversion values at one hour after the start ofthe reaction are shown in Table 1. The reaction was continued underthese conditions, and an elemental analysis of the catalyst taken outafter 100 hours elapse was performed. The results of measurements of theamount of carbonaceous matters on the catalyst are shown in Table 1.

Reaction Conditions

reaction temperature: 1113 K

reaction pressure: 2 MPa

reforming gas: H₂O/CH₄ mole ratio=1 or CO₂/CH₄ mole ratio=1 GHSV=5,000h⁻¹ (W/F=3.85 g-cat·h·mol⁻¹)

total gas supply rate: 19.4 ml/min

catalyst quantity: 0.2 g

EXAMPLE 2

(1) Catalyst Preparation

A 1 mol % rhodium-5 mol % cobalt-magnesium mixed oxide was obtained inthe same manner as in Example 1, with the exception that 0.699 g ofrhodium nitrate was employed in place of the 0.695 g of manganesenitrate hexahydrate.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

EXAMPLE 3

(1) Catalyst Preparation

A 1 mol % ruthenium-5 mol % cobalt-magnesium mixed oxide was obtained inthe same manner as in Example 1, with the exception that 0.964 g oftri-acetylacetonate ruthenium was employed in place of the 0.695 g ofmanganese nitrate hexahydrate.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

EXAMPLE 4

(1) Catalyst Preparation

A 1 mol % platinum-5 mol % cobalt-magnesium mixed oxide was obtained inthe same manner as in Example 1, with the exception that 0.952 g ofbis-acetylacetonate platinum was employed in place of the 0.695 g ofmanganese nitrate hexahydrate.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

EXAMPLE 5

(1) Catalyst Preparation

A 1 mol % palladium-5 mol % cobalt-magnesium mixed oxide was obtained inthe same manner as in Example 1, with the exception that 0.558 g ofpalladium nitrate was employed in place of the 0.695 g of manganesenitrate hexahydrate.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

EXAMPLE 6

(1) Catalyst Preparation

A 1 mol % zinc-5 mol % cobalt-magnesium mixed oxide was obtained in thesame manner as in Example 1, with the exception that 0.720 g of zincnitrate hexahydrate was employed in place of the 0.695 g of manganesenitrate hexahydrate.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

EXAMPLE 7

(1) Catalyst Preparation

A 1 mol % lead-5 mol % cobalt-magnesium mixed oxide was obtained in thesame manner as in Example 1, with the exception that 0.673 g of leadchloride was employed in place of the 0.695 g of manganese nitratehexahydrate.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

EXAMPLE 8

(1) Catalyst Preparation

A 1 mol % lanthanum-5 mol % cobalt-magnesium mixed oxide was obtained inthe same manner as in Example 1, with the exception that 1.05 g oflanthanum nitrate hexahydrate was employed in place of the 0.695 g ofmanganese nitrate hexahydrate.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

EXAMPLE 9

(1) Catalyst Preparation

A 1 mol % cerium-5 mol % cobalt-magnesium mixed oxide was obtained inthe same manner as in Example 1, with the exception that 0.790 g ofcerium (III) nitrate hexahydrate was employed in place of the 0.695 g ofmanganese nitrate hexahydrate.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

Comparative Example 1

(1) Catalyst Preparation

A 5 mol % cobalt-magnesium mixed oxide was obtained in the same manneras Example 1, with the exception that 59.0 g of magnesium nitratehexahydrate was employed, and 0.695 g of manganese nitrate hexahydratewas not used.

(2) Reaction Test

Reaction tests were carried out under the same conditions as inExample 1. The methane conversion value at one hour after the start ofthe reaction, and the amount of carbonaceous matters on catalyst removedafter 100 hours of reaction are shown in Table 1.

TABLE 1 Methane conversion (%) af- Example ter reaction for one hourCarbonaceous matters (wt %) And reforming after reaction for 100 hoursComp. with Reforming Reforming Reforming Example CH₄/H₂O with CH₄/CO₂with CH₄/H₂O with CH₄/CO₂ Ex. 1 47.90 55.60 0.18 0.25 Ex. 2 47.75 55.310.32 0.40 Ex. 3 47.63 55.01 0.38 0.49 Ex. 4 48.01 55.65 0.27 0.35 Ex. 547.94 54.39 0.42 0.60 Ex. 6 46.62 54.74 0.70 0.89 Ex. 7 45.98 50.73 0.881.03 Ex. 8 46.50 49.16 1.41 1.65 Ex. 9 47.03 53.50 1.35 1.59 Comp. 46.2654.61 1.53 1.72 Ex. 1

What is claimed:
 1. A catalyst for reforming comprising a mixed oxide having a composition expressed by: aM.bCo.cMg.dCa.eO in which a, b, c, d, and e are molar fractions satisfying: a+b+c+d=1; 0.0001≦a≦0.10; 0.0001≦b≦0.20; ≦0.9998; 0<c≦0.9998; 0≦d<0.9998; and e=the molar fraction of oxygen necessary to maintain an electric charge balance; and M is at least one element selected from the group consisting of group VIA elements, group VIIA elements, group VIII transition elements excluding Co, group IB elements, group IIB elements, group IVB elements, and lanthanide elements in the periodic table, wherein M and Co are highly dispersed in said mixed oxide.
 2. The catalyst for reforming according to claim 1, wherein M is at least one element selected from the group consisting of manganese, rhodium, ruthenium, platinum, palladium, zinc, lead, lanthanum, and cerium.
 3. The catalyst for reforming according to claim 1, wherein the catalyst for reforming is subjected to an activating treatment which is carried out by heating the catalyst at 773 to 1273 K in the presence of a reducing gas.
 4. The catalyst for reforming according to claim 3, wherein the activating treatment is carried out for 1 to 120 minutes.
 5. The catalyst for reforming according to claim 1, wherein the MgO and CaO in the mixed oxide have a rock salt crystal structure and a portion of each of the Mg and Ca atoms positioned in the lattice of the crystal structure is substituted with cobalt and M.
 6. A catalyst for reforming comprising a mixed oxide having a composition expressed by: aM.bCo.cMg.dCa.eO in which a, b, c, d, and e are molar fractions satisfying: a+b+c+d=1; 0.0001≦a≦0.05; 0.0001≦b≦0.15; 0.85≦(c+d)≦0.9998; 0.35≦c≦0.9998; 0≦d≦0.5; and e=the molar fraction of oxygen necessary to maintain an electric charge balance; and M is at least one element selected from the group consisting of group VIA elements, group VIIA elements, group VIII transition elements excluding Co, group IB elements, group IIB elements, group IVB elements, and lanthanide elements in the periodic table, wherein M and Co are highly dispersed in said mixed oxide.
 7. The catalyst for reforming according to claim 6, wherein M is at least one element selected from the group consisting of manganese, rhodium, ruthenium, platinum, palladium, zinc, lead, lanthanum, and cerium.
 8. The catalyst for reforming according to claim 6, wherein the catalyst for reforming is subjected to an activating treatment which is carried out by heating the catalyst at 773 to 1273 K in the presence of a reducing gas.
 9. The catalyst for reforming according to claim 8, wherein the activating treatment is carried out for 1 to 120 minutes.
 10. The catalyst for reforming according to claim 6, wherein the MgO and CaO in the mixed oxide have a rock salt crystal structure and a portion of each of the Mg and Ca atoms positioned in the lattice of the crystal structure is substituted with cobalt and M.
 11. A catalyst for reforming comprising a mixed oxide having a composition expressed by: aM.bCo.cMg.dCa.eO in which a, b, c, d, and e are molar fractions satisfying: a+b+c+d=1; 0.0001≦a≦0.03; 0.0001≦b≦0.10; 0.90≦(c+d)≦0.9998; 0.6≦c≦0.9998; 0≦d<a0.3; and e=the molar fraction of oxygen necessary to maintain an electric charge balance; and M is at least one element selected from the group consisting of group VIA elements, group VIIA elements, group VIII transition elements excluding Co, group IB elements, group IIB elements, group IVB elements, and lanthanide elements in the periodic table, wherein M and Co are highly dispersed in said mixed oxide.
 12. The catalyst for reforming according to claim 11, wherein M is at least one element selected from the group consisting of manganese, rhodium, ruthenium, platinum, palladium, zinc, lead, lanthanum, and cerium.
 13. The catalyst for reforming according to claim 11, wherein the catalyst for reforming is subjected to an activating treatment which is carried out by heating the catalyst at 773 to 1273 K in the presence of a reducing gas.
 14. The catalyst for reforming according to claim 13, wherein the activating treatment is carried out for 1 to 120 minutes.
 15. The catalyst for reforming according to claim 11, wherein the MgO and CaO in the mixed oxide have a rock salt crystal structure and a portion of each of the Mg and Ca atoms positioned in the lattice of the crystal structure is substituted with cobalt and M. 